Sacred Circles' Coven

Water's Roving Ways

® World and I Magazine 2003

As the precious fluid filling Earth's deepest basins responds with air to solar heating, gravity's pull, and Earth's movement, it flows in great circular currents, waters the continents, and strongly influences climate.

Bottles carrying messages as they drift across the ocean capture the imagination and provide clues to water's roving ways. Benjamin Franklin used such bottles to improve transatlantic communication. As postmaster general for the prerevolutionary colonies, he noticed that postal ships piloted by American former whaler captains were faster than British ships. The differences, he realized, arose because the Americans knew the prevailing currents much better. In a remarkable experiment, Franklin dropped bottles with messages into the Gulf Stream, asking the finders to return them with information on where they had been retrieved. Using data gleaned from both the messages and the whalers, he compiled charts that upgraded mail delivery at the time and still to this day accurately reflect the North Atlantic's circulating motion.

Like no other substance on Earth, water circulates. Driven by gravity, sunlight's heating, night's cooling, air currents, and concentrations of dissolved materials, water moves. As raindrops falling in the high mountains, it begins a great journey to the mother ocean. But water is too adaptable, too versatile and interactive, to follow a simple path. The droplet may never reach a stream: it may first evaporate, moisten a parched lichen, or soak into the ground to be absorbed by the root of a tree. It may soak into sandstone and percolate deep underground, assembling with other droplets into a great pool collected among interstices of buried rocky layers.

Yet multitudes of freshwater droplets do join into tiny streams that converge with others. The mighty rivers they form rush to the sea carrying loads of weathered sediments. Beneath these rivers and the land, unseen by human eye, water flows slowly toward the sea through porous rock, oozing eventually into the ocean through underwater springs.

The restless seas

Where water has puddled into the deepest basins on the planet, forming the oceans, gravity is no longer the major driver of its movements. In them, moving air, solar heating, cooling and loss of fresh water through evaporation, and loss of fresh water through freezing all join gravity in determining water's movements. Despite intrusions of the continental masses, the oceans are all linked into one body, ever seeking to balance imbalanced energy gains and losses to its widespread parts through a complex circulation system.

Much of the balancing occurs in the upper layers within specific ocean basins, such as the North Atlantic basin, in which winds at different latitudes are blowing in opposite directions. The water responds by moving in a roughly circular movement north of the equator, with a major spur also running northeast between Iceland and Europe before it circles back along Greenland's eastern coast. Superimposed and integrated with the horizontal surface currents are vertical currents, whose downflowing and upwelling segments may be separated by thousands of miles and connected by cold currents flowing along the ocean bottom. The vertical currents can be driven by differences of density--water in a current can become more dense with salt as the fresh water evaporates or freezes--or simply by water being blown away from one coast and replaced from below by emerging bottom currents.

Ultimately, water's incessant motion can be traced to energy imbalances produced by solar heating and affecting both water and air as a linked system. To understand the dynamic relations of atmospheric winds and ocean currents, we'll look first at air movements.

Earth, wind, and heat

Wind is simply air moving to redress an imbalance in the air pressure of two different areas. As sunlight hits Earth's surface each day, the land heats faster than the ocean water. The warmed air above the land becomes less dense and rises, creating a partial vacuum (low pressure area) that pulls cooler air (generally resting over the ocean) in toward it. Thus, warm air rising generates the cool breezes typically experienced along the beaches of the world.

On a grander scale, the same process creates large-scale atmospheric currents--wind that travels in more or less constant directions over huge areas. These atmospheric currents, one of the main drivers of ocean currents, are a natural consequence of sunlight striking Earth's curved surface and thereby heating Earth unevenly. Near the equator, where sunlight strikes Earth's surface closest to vertical and with the shortest traverse through the atmosphere, solar heating is significantly greater than it is in the higher latitudes. That same solar influx strikes the surface with less potency at the higher latitudes, because it hits the surface at an oblique angle and is spread over a greater area. Furthermore, because light strikes the higher latitudes at an oblique angle, it is more likely to be reflected back into space, either off clouds or from Earth's surface. The light is also less strong since it has traveled a longer distance through the atmosphere. This tends to disperse the light, as everyone has noticed in comparing the strength of the sun at noon and at sunset.

If no transport mechanism existed to move energy from equatorial regions toward higher latitudes, most high latitudes would be frozen wastelands. There would be no Moscow, London, Paris, Toronto, or any other high-latitude city. Conditions in those locations would be as harsh as those at the North Pole today. Fortunately, atmospheric and ocean currents carry heat energy from the equator to these regions.

As the equatorial regions heat up and ocean waters evaporate, the hot-moist air rises, drawing cooler air from higher latitudes into the tropical regions, which in turn produces low-pressure cells north and south of the equator. The rising tropical air cools through expansion, dumping prodigious amounts of water and nourishing the tropical rain forests. The now dry and cooler tropical air descends around the north and south 30? latitudes. It can move along the surface toward either higher latitudes, as the westerlies, or the equator, as the trade winds. The descending air forms high-pressure regions along these latitudes.

The warm westerly winds moving toward higher latitudes rise over the colder, dense air masses moving away from the poles (the polar easterlies). From the time of the earliest circumnavigators, sailors learned to use these directional currents to power their ships across the seas.

In the Northern Hemisphere, northbound currents of both air and water inevitably curve toward the right. This is due mainly to the Coriolis force, which arises because points at different latitudes move at different speeds as the Earth rotates.

Ocean currents are driven primarily by friction or drag as the atmospheric currents move over the seas, affecting water to a depth of about 300 feet. Some of the wind-driven surface water movements become drivers of bottom currents spanning thousands of miles. They are linked to surface currents in certain zones where vertical water flows are driven by gravity. In a zone east of Greenland, for example, a branch of the Gulf Stream, now cooled and salt-heavy due to loss of fresh water through evaporation and freezing, displaces less-dense waters below it and sinks to the ocean depths. In the eastern Pacific, off the coast of South America, prevailing winds produce a surface water deficit that is replenished by water welling up from the bottom.

Clearly, the oceans' complex circulation patterns begin with wind-driven surface currents. The Atlantic Ocean demonstrates the pattern with two great circular currents, one in the central north and the other in the central south. In the north Atlantic, for example, the trade winds drive the North Equatorial current roughly from West Africa to the West Indies before the water flow curves north to become the Gulf Stream, running north and east across the Atlantic. The current splits in mid-ocean, with the North Atlantic current, driven by the westerlies, continuing northeast between Iceland and northern Europe. The other branch circulates toward the south as the Canary current, which completes the circuit by joining up with the North Equatorial current.

Currents in the North Atlantic, then, are completing a circular flow pattern in a clockwise direction, thanks to both the Coriolis effect (air and water currents move along curved paths) and the prevailing winds at different latitudes (trade winds nearer the equator blowing toward the west and westerlies further north blowing toward the east). In the Northern Hemisphere, the large circular cell, or gyre, defined by the ocean currents rotates clockwise; its counterpart in the Southern Hemisphere rotates counterclockwise. Water tends to converge toward the center of the gyres, creating "hills" on the ocean's surface.

Major surface currents in the Atlantic have been well known for decades, and these currents have been incorporated into explanations of climate patterns of North America and western Europe. In an apparently clear example, standard wisdom for decades has been that British winters are moderated by tropical heat transported northward by the Gulf Stream. Recent studies published in the September 27, 2002, issue of Science challenge this view. Researchers who analyzed meteorological observations made over the past 50 years have concluded that roughly 80 percent of the heat carried to Ireland and Britain by transatlantic winds was derived not from heat carried by the Gulf Stream but rather from summer heat stored briefly in the ocean. The winds blow into Europe across the ocean from the southwest carrying heat retained by the ocean waters into the winter months, when the land has cooled much more rapidly.

The finding does not challenge any of the basic facts about the Gulf Stream, only its role in climate. In the bigger picture, however, nothing is changed: water and wind are still collaborators in heat transport that moderates temperature extremes toward the planet's poles.

Climate

Climate is complex and still poorly understood. Nonetheless it is clear that atmospheric and oceanic currents must be included among the many factors affecting climate. Even more fundamental to climate than currents are some of the planet's more fixed geophysical factors, especially seasonal changes caused by the tilt of Earth's axis and such effects of the continents as constraining circulation patterns and heating the air. As noted earlier, continental crust warms up faster than juxtaposed oceans because the crust's heat capacity is lower than that of water. Although water takes longer to heat up than crustal rock does, it loses heat more slowly. In summer, the crust will heat up faster than adjoining ocean water, and in winter it will lose the heat more rapidly. As a result, temperatures in the interior of the continents are colder in the winter and warmer in the summer than those in climates at equal latitudes along the coast.

During the summer months, as the continents and overlying air heat up, the hot air rises, creating low-pressure cells. The opposite occurs in the winter, when cold and dense--and thus heavy--air forms high-pressure belts over the continents. The low-pressure cells centered over Asia during the summer pull the moist atmospheric currents from the Pacific, which in turn leads to the downpours associated with the monsoon season.

North America's climate follows the basic continental pattern, with low-pressure cells predominating in the summer and high-pressure cells predominating in the winter. Played out between reservoirs of tropical air and polar air, these changing continental cells often force air masses from the high and low latitudes into contact with themselves, producing tempests along the fronts (that is, the contact zones between cells). In the summer, for example, the continental low-pressure cells draw tropical high-pressure cells with their high moisture load onto the continent. Active storm fronts form where the low- and high-pressure cells meet, and the moisture is dropped.

The tropical and polar air masses that invade North America tend to travel in an easterly direction because they interact with the eastward-moving jet stream five to eight miles above the surface. The jet stream is a fairly consistent wind that zigzags across North America, Europe, and Russia in its path around the world. As it sways across the continents, the jet stream directs warm air toward the higher latitudes during the summer (the summer low-pressure cell over the continents) and cold air toward the south in the winter (the winter high-pressure system).

El Nino

Across the vast, tropical Pacific Ocean, wind and water are intimately linked and implicated in a pas de deux with global consequences literally for feast or famine.

When the easterly trade winds blow strong from South America to Indonesia, as they usually do, warmer surface waters pile up on the western shores of the basin. The surface water deficit along the basin's eastern shores is replenished by the upwelling of colder bottom waters, especially along the coasts of Peru. If the easterly trade winds slacken or reverse direction, as they do every four to seven years, water again responds and world climate enters the time of an El Ni?o. During El Ni?o, water levels in the Pacific basin even out, warmer surface waters move toward South America, upwelling along the continent's western margins ceases, and rainfall patterns shift around the world.

Some details flesh out the contrast between the two main dance steps--either strong or slack easterly trade winds--performed by wind and water in the tropical Pacific basin. When the easterly trade winds are strong, water levels can be a half yard higher off the coast of Indonesia than off Peru, and downwelling occurs along the coasts of Australia and Indonesia. The warm waters in the western Pacific generate rising moist air that contributes to normal seasonal rainfall along eastern Australia and Indonesia. In contrast, the surface currents flowing away from Ecuador and Peru cannot be compensated for by an equal amount of surface water flowing into the area, so water comes from below, creating the upwelling effect.

The upwelling currents carry an abundance of plankton and other nutrients that have died and sunk to the ocean floor. Along the coasts of Ecuador and Peru, the cold upwelling waters feed a host of fish species, including the anchovy, which is the staple of Peru's fishing industry. The waters are some of the richest in the world. Once a year around December, the trade winds diminish and the surface waters remain in place, preventing the rise of the upwelling currents. Typically, the conditions last for only a few months. The warm waters near the South American coast generate rains that cause flooding as they move inland throughout northwestern South America. Meanwhile, the waters off the coasts of Australia and Indonesia remain cold, creating droughts in the region.

At times, the conditions last for extended periods, sometimes for years, affecting climatic conditions on not only the margins of the central Pacific Peru but also the entire Earth in what can only be considered a domino effect. The fishermen of these waters christened the weather upheaval El Ni?o (in Spanish, the "little one") because it occurs near or during the Christmas season. Recent records indicate that large El Ni?os occurred in 1982--'83, 1986--'87, 1991--'92, and 1997--'98.

The El Nino of 1982--'83 serves as an excellent example of the devastating weather that can result from a series of chain reactions felt around the globe. Australia endured the worst drought of the century, which generated continual dust storms. One that hit Melbourne extended thousands of feet into the sky and stretched across 300 miles, dumping a half-million tons of rich topsoil over the city. The drought also caused innumerable fires as the bush withered. Farmers were faced with kangaroo stampedes as the animals desperately tried to quench their thirst and hunger, reducing already depleted water supplies and crops.

During this period the typically dry coasts of Ecuador and Peru were drenched with water, culminating in flash flooding, which tore away soil loosely anchored by sparse vegetation. Near Chunchi, Ecuador, mudflows killed over 100 people. Tahiti, a fair-weather island, was ravaged by six cyclones in five months. As the domino effect moved to the northern latitudes, drought struck parts of Africa, causing widespread famine. Local flooding occurred along the Mississippi River as rains soaked the Gulf states. Only the continents of Europe and Antarctica went untouched by the changing weather conditions.

The good news is that scientists can now predict the coming of extended El Ni?os by monitoring ocean-water temperatures. The National Oceanic and Atmospheric Administration has deployed a series of buoys extending across the Pacific that transmit water temperatures to scientists around the world.

Watering the continents

The sun shines. The winds blow. The currents flow. Air circulates. Water circulates.

Land is different. In comparison to air and water, its tectonic cycles count as no movement. Land impedes water's movements. It impounds water in lakes or underground reservoirs and even slows rivers rushing to the oceans.

Land adds a new dimension to global water cycles: fresh water. Without land, the purified water in the clouds would fall back into the salty sea. Land also adds complexity and richness to the water cycle, supporting the plants and animals that regularly circulate water through their systems and incorporate it as their primary constituent.

For the needs of plants and animals, ocean currents, prevailing winds, evaporation, high-pressure and low-pressure cells, and the jet stream are unreliable suppliers of fresh water. Although they deliver fresh water with regularity in some places, they more commonly deliver it in bursts and dearths. Land compensates for water's irregularity, evening out both the floods and the droughts and also the more regular annual cycles, in which days or weeks of abundant water supply alternate with days or weeks of scarce supply.

Adapting to water's fleet cycles by taking advantage of the land's impoundments and impediments is a great challenge for life that demands a regular freshwater supply. Although plants and animals have already adapted themselves to meet that challenge, humans have yet to meet it in a way that goes beyond brute-force expropriation of irreplaceable ancient reservoirs and fouling running waters or completely depleting them.

As twenty-first century society faces the challenge of enhancing or maintaining its fresh-water supplies, it can take a lesson from Benjamin Franklin. By mapping the prevailing ocean currents and directing his postal ships to follow or avoid them, he worked within the constraints of the prevailing currents.

Science today provides a wealth of detail about global water cycles, prevailing currents that extend across oceans and continents and across timescales ranging from years to millions of years. These cycles collectively define prevailing currents constraining global society. Like Franklin, we need to learn to work within them.

Written permission from original author is needed to reprint. Articles within are used w/permission, or are originals.

We do have some older pages have within that are with Author Unknown? If you know of the original author, please contact any one of us and we will give the Proper Credits.

http://sacredcirclescoven.com

**Site Maintained and Created by Lady Leona

Owned Exclusively by Sacred Circles' Coven. Witch HPs Leona

Orginally Founded Oct 15, 2002, Mother site Originally Founded Aug 1, 2000.

Hosted by BlueHost.com